1. Field of the Invention
The present invention relates to inflatable airbags for protecting vehicle occupants during collision events. More specifically, the present invention relates to an expandable rigid knee airbag system that facilitates proper occupant positioning in order to reduce lower leg and other injuries in vehicle collisions.
2. Description of Related Art
Inflatable airbags enjoy widespread acceptance as passive passenger restraints for use in motor vehicles. This acceptance has come as airbags have built a reputation of preventing numerous deaths and injuries over years of development, testing, and use. Studies show that in some instances, the use of frontally placed vehicular airbags can reduce the number of fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Other statistics suggest that in a frontal collision, the combination of a seat belt and an airbag can reduce the incidence of serious chest injuries by 65% and the incidence of serious head injuries by up to 75%. These numbers and the thousands of prevented injuries they represent demonstrate the life-saving potential of airbags and the need to encourage their use, production, and development.
As a result in part of benefits such as those described above, automakers are now required to install airbags in most new vehicles manufactured for sale in the United States. Many automobile manufacturers have turned this airbag technology requirement into a marketing tool. Enticed by the promise of added safety, vehicle purchasers frequently seek out vehicles with sophisticated airbag systems.
Airbags are often installed in the steering wheel and in the dashboard on the passenger side of a car. These airbags are generally large and thick. They are used for the primary deceleration of a vehicle occupant since, in a large fraction of collisions, the occupant is accelerated forward through the vehicle. Such airbags are generally housed within the dashboard, steering wheel, or other similar interior panels of a vehicle, and are covered by a trim cover panel. The trim cover panel covers the compartment that contains the airbag module. Such airbag covers are typically made of rigid plastic, and are configured to be opened by the pressure created by the deploying airbag. During deployment of the airbag, it is preferable to retain the airbag cover in at least partial attachment to the vehicle to prevent the airbag cover from flying loose in the passenger compartment. If the airbag cover were allowed to detach and freely move into the passenger compartment, it could cause injury to a passenger.
Airbags may be mounted in vehicular panels near the steering wheel, in the region or components of the glove box, in vehicle doors, along vehicle roof rails, walls, vehicle floors, or beneath a dashboard to provide deceleration in specific types of collision events.
Airbags are generally linked to a control system within the vehicle that triggers their initiation when a collision occurs. Generally, an accelerometer within the vehicle measures the abnormal deceleration caused by the collision event and triggers the ignition of an airbag inflator. This control system is often referred to as an electronic control unit (or “ECU”). The ECU includes a sensor that continuously monitors the acceleration and deceleration of the vehicle and sends this information to a processor which processes it using an algorithm to determine whether a deceleration experienced by the vehicle is a collision or not.
When the processor of the ECU determines, based on a set of pre-determined criteria, that the vehicle is experiencing a collision, the ECU transmits an electrical current to an initiator assembly connected to an inflator that is coupled to the airbag module. The initiator activates the inflator. An inflator is a gas generator that typically uses a compressed or liquefied gas or a mixture of gases, a solid fuel, or some combination of the two, to rapidly generate a large volume of inflation gas. The gas is then channeled, often through a segment of specialized tubing called a gas guide. The gas inflates the airbag, thus placing it in the path of the vehicle occupant and allowing it to absorb the impact of the vehicle occupant.
As experience with the manufacture and use of airbags has progressed, the engineering challenges involved in their design, construction, and use have become better understood. First, most airbag systems are designed to rapidly inflate and provide a cushion in front of or alongside an occupant based on a presumption that the occupant will be in a predetermined position. Problems have been noted to occur when the occupant is “out of position” in regard to this presumed placement when a collision event occurs and the airbag deploys. Similarly, problems may occur when the occupant, though possibly at first in the predicted position, strikes a glancing blow to the airbag, and is then deflected out of the airbag before proper deceleration can occur.
Out of position injuries may be attributed in part to the fact that most airbag systems have been primarily designed for deployment in front of the torso of an occupant. More specifically, such airbags are disposed for deployment between the upper torso of an occupant and the windshield and instrument panel. During a front-end collision, there is a tendency for an occupant, particularly one who is not properly restrained by a seat belt, to slide forward along the seat. This results in poor kinematics and positioning when the occupant interacts with a frontal airbag such as a driver's side or passenger's side airbag.
In order to avoid such dangers to occupants, knee airbag systems have been developed. These airbags deploy during a collision event and engage an occupant's knees or lower legs. This holds the occupant in place on the seat, and improves the kinematics of the occupant.
Such knee airbag systems include a knee airbag and a panel, referred to as a knee bolster panel, which is disposed in front of the knee airbag. The knee bolster panel provides a more rigid surface area than an airbag would alone to better engage and decelerate the knees or legs of an occupant and thereby restrain the occupant's lower body. Additionally, the knee bolster panel allows some degree of deformation to minimize the impact to an occupant.
Such knee bolster airbag systems, like many other airbag systems, suffer from high cost and engineering problems. Specifically, knee bolster airbags are difficult to design to be mounted in the tight spaces available under the steering column or dashboard in order to be properly positioned to contact a vehicle occupant's knees. Further, many current knee airbag systems use an inflator located at a remote location. Such systems require the use of costly gas guides suitable for conducting hot inflation gases from the inflator to the airbag. Additionally, the airbags themselves must be treated with various coatings to protect the fabric of the airbag itself from the heat of the gas. Yet further, airbag inflators must be made to include baffles and filters to act as heat sinks for the inflation gas of the inflator. These elements add bulk to the inflator, thus increasing its space requirements, and also add expense to the cost of the inflator. Finally, in some specific applications, such as mounting an airbag in the door of a glove box of a vehicle, fabric airbags have proven very difficult to install.
It is thus understood that it would be an advancement in the art to provide an expandable rigid knee airbag system to protect a vehicle occupant in collision events in a wide variety of situations. Specifically, it would be an advancement in the art to provide a knee airbag suitable for mounting in a vehicle under the steering column or dashboard, including mounting in a glove box door. Additionally, it would be an advancement in the art to provide a knee airbag system with heat resistance to allow the use of a low-cost pyrotechnic inflator and permit direct mounting of the inflator to the airbag and to avoid the expense added to an airbag system by gas guides, inflator baffles, and inflator filters. Such a device is disclosed and claimed herein.